|
(including
Werding-Hoffmann Disease and
Kugelberg-Welander Disease)
WHO IS
AFFECTED?
SMA is one
of the most prevalent genetic disorders.
Spinal muscular atrophy (SMA) is a genetic, motor
neuron disease characterized by wasting of the skeletal
muscles caused by progressive degeneration of the
anterior horn cells of the spinal cord. The disorder
causes weakness and atrophy of the voluntary muscles.
Weakness occurs more often in the legs than in the arms.
There are many types of SMA. Most types, however, are
extremely rare, occurring in only one or two families.
Some of the more common types are briefly described
below.One
in every 6,000 babies is born with SMA. Of children
diagnosed before age two, 50 percent will die before
their second birthday.SMA can strike anyone of any age,
race or gender.One in every 40 people carries the gene
that causes SMA. The child of two carriers has a one in
four chance of developing SMA.
THE TYPES
OF SMA
Type I,
or Werdnig-Hoffman
Disease, is the most severe form of SMA. Children
with Type I tend to be weak and lack motor
development, rendering movement difficult. Children
afflicted with Type I cannot sit unaided and have
trouble breathing, sucking and swallowing. Type I
SMA strikes infants between birth and six months.
Type II,
is slightly less
severe. Type II patients may be able to sit unaided
or even stand with support and usually do not suffer
from feeding and swallowing difficulties. However,
they are at increased risk for complications from
respiratory infections. Type II SMA affects infants
between seven and 18 months old.
Type III,
also known as Kugelberg-Welander Disease, is the
least deadly form of childhood-onset SMA. Type III
patients are able to stand, but weakness is
prevalent and tends to eventually sentence its
victims to a wheelchair. Type III SMA strikes
children after the age of 18 months, but can surface
even in adulthood.
Type IV,
is the adult form of the disease in which symptoms
tend tobegin after age 35. Symptoms usually begin
in the hands, feet and tongue, and spread to other
areas of the body.
Adult Onset X-Linked SMA, also known as
Kennedy's Syndrome or Bulbo-Spinal Muscular Atrophy,
occurs only in men. Facial and tongue muscles are
noticeably affected. In addition, these men also
often have breast enlargement known as
gynecomastia. Like all forms of SMA, the course of
the disease is variable, but in general tends to
progress slowly.
SMA does
not affect sensation and intellectual activity in
patients. It commonly is observed that patients with SMA
are unusually bright and sociable.
RESEARCH
In 1999,
investigators at The Ohio State University replicated
SMA in a mouse model. The researchers have demonstrated
that when the mice have high amounts of the SMN2 gene,
which is present in all human SMA patients, the SMA
phenotype is corrected and they develop normally. These
findings support the conclusion that large amounts of
the protein could act to prevent the damage caused by
SMA or even reverse the impact of the disease.
Since then, many more important
research steps have been made. For
details, please see
SMA Research.
This research was funded in large
part by the volunteer driven, not-for-profit
organization Families of SMA -
http://www.fsma.org/
TESTING
Prenatal
counseling is available to couples who are carriers of
SMA or who have lost a child to SMA. |
